> Pomax is approaching the vanishing points exponentially rather than hyperbolically

Exactly this. To put it in drawing terminology, the distance of a line towards the vanishing point is related to the angle from the camera (station point) projected back to the picture plane. Images like this may be of assistance for those of a computer and not hand drawing background https://guidetodrawing.com/site/assets/files/1082/gtd-235.79...

An exponential ratio as used by the article could maybe be described as assuming the camera is 0 distance from every point drawn.

[Edit: Really great article though - the kind of thing I love to see is looking at a complex problem with established solutions from first principles again]